I use a tabbed telnet/SSH app called ZOC. From there I can specify the telnet ports and which switch they map to. I can now console into all of them without the need of a terminal server. The actual USB-Serial cables only cost me £2 each, and you can have loads of them.

47 thoughts on “Why buy a terminal server when an old PC will do”

Just curious:
– any particular reason you don’t use a dedicated management VLAN to connect yourself to your switch ?
– what connection model do you choose to connect your dynamips routers to your switches ? Quad-NICs or Q-in-Q ?

Laurent
- Yes. In labbing environments you always use the console. Mainly as every lab would require you to start from scratch. That means at the end of every lab you’re going to be doing a wr erase. This means every lab you’ll have to log back on via the console and have to redo your management vlan configuration again. With the console, you never have to worry about losing connection in the middle of your lab

- I’m using Quad NIC’s. I don’t want to have to buy an extra switch just to do QinQ. The NIC’s are cheaper and they just look better

Hi,
There is something I don’t understand in the cabling.
The USB-Serial cable is plugged into the serial port of the dynamips box.
The roll over cable is plugged into a switch console port.
What happens between this two ends ?

I thought rollover cable had one rj45 connector on each side.
The famous blue console cable with a rj45 at one end and a serial at the other end is also called rollover cable. Am i right ?

Now it all make sense.
The USB-Serial cable is plugged into the USB port of the dynamips box. The serial connector is linked to serial connector of the rollover cable and finally the rj45 connector of rollover cable is plugged into the console port of the switch.

I’d been puzzling over how to solve this one cheaply for a while (and kicking myself for selling that 2511RJ sometime back). I ended up buying a couple of USB to 4x Serial adapters. (eg http://www.amazon.co.uk/NEWLink-Serial-Quad-Cable-Adaptor/dp/B003DA5TG4) There are also USB to 8x Serial available.
Whilst not the tidiest of solutions it’s better than a usb hub plus multiple single usb to serial adapters. Works a treat with cisco serial cables or a null modem cable (for those pesky olives ;-)
Using /usr/bin/screen to drive the whole thing is also a big win over minicom or cu. Simply screen /dev/ttyUSBx and you’re there. (if you need a different data rate put it after the device eg screen /dev/ttyUSB3 115200
HTH

I’m trying to implement a rack rental facility for study purposes at my university. Your post really helps as I can avoid buying an access server. However, would you have any ideas as to how I could perhaps do what you have done and interface with a WAN environment. For instance, have several terminal sessions running, each connected to one device’s console – any idea how I could say provide users with my IP address and a port number so that when they telnet/ssh, they’re straight into the terminal?

I don’t see why this couldn’t be extended to multiple racks. The big thing is you would need enough serial ports for all your devices. I would probably go for those 4 port serial to 1 port usb devices. Get a bunch of them in.

Then let’s say you have Rack1 going to ports 2000-2010, Rack2 going to 2011-2020 and so on.

People then just need to telnet to your public IP address and the port number and they’ll be right on the device :)

but why it will not work using USB HUB ? in this case how can I access 4 switches at the same time from the laptop ?? I am running virtual routers in GNS and 4 physical switches.. I am able to access all virtual routers via console from the telnet router and I will access all 4 physical switches from the same telnet router just typing the SW1 etc…

and about the USB HUB, this is also tested I use the USB HUB with 7 USB ports and I connected 5 physical switches to the HUB and it works like a charm…
Each time I connect the new USB I receive USB0, USB1, USB2 etc….

I am using the USB-to-SERIAL converter model: ATEN (RS-232) ..

and the config below is used in the “ser2net” which I have installed in Ubuntu:
apt-get install ser2net

I installed ser2net and edited the ports, but didn’t know how to save changes, and exited terminal by closing it. Sorry I’ve been searching around and I am lost! Now every time I try the command sudo vi /etc/ser2net.conf it gives me an error: “swap file etc/.ser2net/conf.swp already exists” and I don’t know how to delete that file either!!! I got about 5 swap files… any ideas?? sorry I am just trying new things and I am breaking others!!!! Any help really appreciated

Hi Addy. The swp file is there because you have closed your terminal session with the file still open. vi can be a little bit funny to use so I would reccomend using gedit if you’re using a gui. Open the file there and save. Then reload ser2net and it should work

I was working on this exact same thing. I am glad you posted how you set yours up. I was curious if you had any issues with the Com ports remaping themselves (eg, after a reboot). Are you able to consistently reach the same adapter? I am just nervous that after mapping all of my devices I would have to figure out what one is what if I shut down my machine. I would appreciate your imput. Thanks.

Thanks for the advice. Saved me money on a console server.
I am running into a problem. Everytime I reboot my ubuntu box my usb adapters get new USBtty numbers. Is there anyway to statically assign a USBtty number to a usb to serial adapter?

I set this up on a raspberry pi using two quad serial to USB adaptors hanging off a powered USB hub on the Pi, then made up 7 serial to RJ45 socket rollover adaptors and run straight through cat-5 to each console port on the switches, worked a treat – Thanks for this info – really helped me out!